1. Field of the Invention
The present invention relates to a milling process for converting large particle size crude quinacridones to pigmentary grade material.
2. Prior Art
U.S. Pat. No. 2,402,167 discloses salt milling crude organic pigments in a ball mill to produce pigmentary grade material.
U.S. Pat. No. 2,816,114 discloses agitating a crude organic pigment with borax, water and a dispersing agent to produce pigmentary grade material.
U.S. Pat. No. 3,657,248 discloses salt milling crude quinacridone in the presence of a phase directing agent to reduce its particle size and produce beta-phase quinacridone.
U.S. Pat. No. 4,287,000 discloses salt milling oversize crude organic pigment in the presence of an organic conditioning liquid.